It is known to provide pressure vessels for nuclear reactors which are hermetically sealed in a single piece and which, when subjected to an excessive internal pressure or explosion, tend to crack with axial rupture lines. Since the stress distribution in such vessels is such that an uncontrolled cracking or rupture of the vessel occurs, the pressure release may be too sudden and catastrophic.
Accordingly, it has been proposed heretofore, to constitute the pressure vessel of a stack of annular cast-metal members which are stressed together by tension elements, e.g. rods or cables, which control the separation of the cast members at the horizontal junctions which form preferred pressure-release sites in the event of a catastrophic or sudden pressure buildup within the interior of the vessel. The stack is generally lined internally with a steel liner welded together from sections.
In practice, the yieldability of the tension rods or cables, which are composed of steel, is about 2% while the yieldability of the steel liner is 20 - 30% so that pressure release at the horizontal seams or junctions cannot be guaranteed because of uncontrolled rupture of the liner. This, of course, defeats one of the primary reasons for using the case-metal annuluses in the first place.
More specifically, a pressure vessel of the latter type does not ensure a readily controllable pressure dissipation in the event of a catastrophe because pressure release does not always occur uniformly at the horizontal junctions which spread against the resistant force of the tension elements.